Atrial stretch measurement for atrial fibrillation prevention

Abstract

A stretch-measurement probe includes an elongate outer sleeve, expansion feature associated with a distal portion of the outer sleeve, and an elongate inner rod disposed at least partially within the outer sleeve. The expansion feature is configured to allow a longitudinal distance between a proximal end of the outer sleeve and the distal end of the outer sleeve to be varied.

What is claimed is: 
     
       1. A method of monitoring stretch in an organ, the method comprising:
 attaching a first magnet to an exterior surface of a right atrium of a heart of a patient at a first position; 
 attaching, separately from the first magnet, a second magnet to the exterior surface of the right atrium at a second position, the second position being spaced from the first position by a first distance; 
 introducing an intravenous bolus of saline fluid into a blood vessel of the patient; 
 using an array of Hall Effect sensors of a monitor device, through a closed chest wall of the patient:
 sensing a post-bolus position of the first magnet; and 
 sensing a post-bolus position of the second magnet; 
 
 determining a post-bolus distance between the first magnet and the second magnet caused by stretching of the atrium in response to the intravenous bolus of saline fluid, the post-bolus distance being greater than the first distance; 
 calibrating an alarm setpoint based on the post-bolus distance; 
 using the array of Hall Effect sensors of the monitor device, through the closed chest wall of the patient:
 sensing a third position of the first magnet; and 
 sensing a fourth position of the second magnet; 
 
 determining a second distance between the first magnet and the second magnet based on the third position and the fourth position; and 
 triggering an alarm based on a determination that the second distance is greater than the post-bolus distance. 
 
     
     
       2. The method of  claim 1 , further comprising:
 determining a baseline blood pressure prior to introducing the intravenous bolus of saline fluid distance between the first magnet and the second magnet; and 
 determining a post-bolus blood pressure after introducing the intravenous bolus of saline fluid; 
 wherein said calibrating the alarm setpoint is based on at least one of the baseline blood pressure or the post-bolus blood pressure. 
 
     
     
       3. The method of  claim 1 , wherein:
 said attaching the first magnet and the second magnet to the exterior surface of the right atrium is performed through an open-chest access to the heart; and 
 said determining the second distance is performed post operatively when a chest of the patient is closed. 
 
     
     
       4. The method of  claim 1 , wherein said determining the second distance between the first magnet and the second magnet is performed external to a body of the patient. 
     
     
       5. The method of  claim 1 , wherein the intravenous bolus of saline fluid comprises at least 100 mL of saline fluid. 
     
     
       6. The method of  claim 1 , further comprising interrogating a radio-frequency identification (RFID) tag associated with at least one of the first magnet or the second magnet. 
     
     
       7. The method of  claim 1 , wherein:
 the monitor device is secured to a chest of the patient using at least one of an adhesive pad or a strap; 
 each of the array of Hall Effect sensors is associated with one of a plurality of light sources, the plurality of light sources having a brightness characteristic that is based on a proximity of a respective Hall Effect sensor to one of the first magnet or the second magnet; and 
 output of ones of the plurality of light sources provides a visual indication of positions of the first and second magnets. 
 
     
     
       8. The method of  claim 1 , wherein the monitor device comprises a display configured to display a representation indicating an actual physical position behind the monitor device of at least one of the first magnet or the second magnet. 
     
     
       9. The method of  claim 1 , further comprising attaching a third magnet to the exterior surface of the right atrium of the heart, wherein said triggering the alarm is further based on a determination that the third magnet has increased in separation distance from the first magnet. 
     
     
       10. A method of monitoring stretch in an organ, the method comprising:
 accessing a heart of a patient; 
 implanting a first sensor device including a first inductive coil on a surface of an atrium of the heart; 
 implanting a second sensor device including a second inductive coil on the surface of the atrium; 
 introducing an intravenous bolus of saline fluid into a blood vessel of the patient; 
 using a monitor device, through a closed chest wall of the patient:
 inductively sensing a post-bolus position of the first sensor device; and 
 inductively sensing a post-bolus position of the second sensor device; 
 
 determining a post-bolus distance between the first sensor device and the second sensor device caused by stretching of the atrium in response to the bolus of saline fluid based on the post-bolus position of the first sensor device and the post-bolus position of the second sensor device; 
 using the monitor device, through the closed chest wall:
 inductively sensing a first position of the first sensor device; and 
 inductively sensing a second position of the second sensor device; 
 
 determining a first distance between the first position and the second position; and 
 providing an alarm output in response to a determination that the first distance exceeds the post-bolus distance. 
 
     
     
       11. The method of  claim 10 , further comprising:
 suturing the first sensor device to the surface of the atrium through an aperture of the first sensor device; and 
 suturing the second sensor device to the surface of the atrium through an aperture of the second sensor device. 
 
     
     
       12. The method of  claim 10 , wherein the alarm output comprises at least one of blinking light output or audible alarm output. 
     
     
       13. The method of  claim 10 , further comprising wirelessly powering the first and second sensor devices using an inductive coil of the monitor device. 
     
     
       14. The method of  claim 10 , further comprising:
 determining a second distance between the first sensor device and a third sensor device implanted on the surface of the atrium; and 
 determining a third distance between the second sensor device and the third sensor device. 
 
     
     
       15. The method of  claim 14 , wherein the first sensor device, the second sensor device, and the third sensor device are arranged in a triangular arrangement on the surface of the atrium. 
     
     
       16. The method of  claim 10 , wherein the first sensor device comprises a magnet.